A concept formed at the turn of the twentieth century that describes the properties of neurons, the specialized cells that make up the nervous system. The neural doctrine was one of the two main theories about the structure of the nervous system at the time. Proponents of the neural doctrine argued that the nervous system consists of discrete cellular units. Proponents of the alternative reticular theory, on the other hand, argued that the entire nervous system is a continuous network of cells with no gaps or synapses between them. In 1873, physician and proponent of the reticular theory Camillo Golgi developed a staining technique called the black reaction, a method of staining neurons that allowed nerve cells to be fully visualized, allowing scientists to see the entire neuronal cell and its cellular structure. Later, the neuroscientist Santiago Ramón y Cajal used the black reaction to show the existence of synapses, or gaps between neurons, and claimed that his evidence supported the neural doctrine. Confirmation of the neural doctrine showed that neurons function as separate and independent cells, rather than as a single network in the nervous system.